Ferrite microwave phase shifter with insertion phase modifying means

ABSTRACT

An apparatus for modifying the insertion phase of a ferrite microwave phase shifter. A plurality of transverse metal plates are inserted into the waveguide to change the insertion phase. At least two plates are inserted into the waveguide through slots separated by a predetermined distance to keep the VSWR to a minimum. Each pair of plates introduces a predetermined amount of phase change. A sufficient number of pairs of plates are inserted to bring the insertion phase of the phase shifter within an allowable range of deviation from an ideal figure.

United States Patent Dixon et al.

FERRITE MICROWAVE PHASE SHIFTER WITH INSERTION PHASE MODIFYING MEANS Inventors: Earl Dixon, Voorhees Twp.;

Norman Richard Landry, Willingboro, both of NJ.

The United States of America as represented by the Secretary of the Navy, Washington, DC.

Filed: Dec. 8, 1972 Appl. No.: 313,229

Assignee:

US. Cl. 333/31 A, 333/24.1 Int. Cl. I-I0lp 1/18 Field of Search 333/24 G, 24.1, 31 A References Cited UNITED STATES PATENTS l0/l969 Reuss, Jr 333/24.l X 10/1972 I-lrivnak et al. 333/241 X Jan. 29, 1974 OTHER PUBLICATIONS Southworth, Principles & Application of Waveguide Transmission, Van Nostrand Co N.Y., 1961, pg, 246, 247 relied on, QC661S68.

Primary Examinerffa ul L. Gensler Attorney, Agent, ofFirm-Jif SYSciascia; P. Schneider; P. Palen ABSTRACT An apparatus for modifying the insertion phase of a ferrite microwave phase shifter. A plurality of transverse metal plates are inserted into the waveguide to change the insertion phase. At least two plates are inserted into the waveguide through slots separated by a predetermined distance to keep the VSWR to a minimum. Each pair of plates introduces a predetermined amount of phase change. A sufficient number of pairs of plates are inserted to bring the insertion phase of the phase shifter within an allowable range of deviation from an ideal figure.

12 Claims, 4 Drawing Figures FERRITE MICROWAVE PHASE SHIFTER WITH INSERTION PHASE MODIFYING MEANS BACKGROUND OF THE INVENTION The present invention relates generally to the field of microwave phase shifters and more particularly to antenna phase shifters for phased array antennas utilizing ferrite materials. I

A phased array antenna system employs a plurality of radiating elements which are electronically scanned. That is, by varying the phase of the respective signals fed to the individual radiating elements, the composite radiated beam can be caused to scan back and forth without mechanical movement of the antenna itself.

Such electronically scanned antenna arrays are often made using ferrite phase shifters. Generally, these devices comprise a rod of ferrite material mounted within a waveguide section and means for producing a magnetic field surrounding the material. By varying the strength of the magnetic field, the phase shift caused by the ferrite rod can be varied. Thousands of these phase shifters may be used in a single large phased array antenna system. The design of phase shifters is based on a fixed set of parameters. The large quantity of phase shifters for each phased array antenna are designed using the same set of parameters. If there is considerable deviation in the parameters or properties of the finished device, it is rendered unusable for its designed function. One parameter which has been particularly difficult to control in the manufacture of prior art ferrite phase shifters is insertion phase; that is, the phase change caused to the microwave by the mere introduction of the ferrite rod into the waveguide. From unit to unit, the insertion phase in a given magnetic reference state must be within a certain percentage of the mean insertion phase of the optimum designed phase shifter.

Workers in the art have experienced great difficulty in obtaining a large number of ferrite phase shifters whose characteristics are all within a deviation small enough to permit their use together in a phased array antenna. The problem arises from the fact that the processing involved in producing ferrite material for use in a phase shifter does not consistently yield a product with properties that are uniform from batch to batch, nor even within the same batch of processed material. The state of the art is such that many factors of the process contribute to the final properties of the material, such as sintering cycle, milling rate, volume of material vs. volume of milling container, density, etc. Experience has shown that even for a small number of batches there can be considerablevariation in magnetic properties of the product. Therefore, for large scale production as required by the typical phased array, the variations in the properties of the individual ferrite rods become meaningful in terms of yield or cost by causing a large percentage of the finished phase shifters to exceed allowable deviations.

SUMMARY OF THE INVENTION The present invention provides a solution to the problem of the large deviations in the insertion phase of ferrite phase shifters. One side wall of the waveguide is provided with a number of vertical slots at a predetermined distance from each other. A pair of metal plates can be disposed in certain of the slots to form inductive irises in the waveguide and provide a predetermined phase advance with a minimum VSWR. The assembled phase shifter is easily and quickly checked for insertion phase by standard testing methods. If the insertion phase is beyond the allowable deviation, one or more pairs of plates are inserted into the slots to bring the phase within the allowable deviation.

Implementation of the present invention in the production of phase shifters results in reduced cost of an antenna array by providing a higher yield of acceptable phase shifters. The plate unit can be inserted quickly and easily during production. It provides good electrical performance and its construction is simple and inexpensive.

OBJECTS OF THE INVENTION An object of the present invention is to provide an apparatus for increasing the yield of useful products in the manufacture of ferrite phase shifters.

Another object of the invention is to provide a simple, inexpensive means to compensate for variations in the electrical properties of ferrite phase shifters.

A further object of the invention is to provide a ferrite phase shifter which can be easily and simply adjusted during production for variations in insertion phase.

Other objects, advantages, and novel features of the present invention will become apparent from the following detailed description when considered in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIGS. 1 and 2, waveguide section 10 has slots 18, 20, 22 and 24 in one vertical wall. Waveguide section 10 forms, with ferrite rod 32, a microwave phase shifter. The magnetic field producting means comprises no part of the invention and is not shown on the drawing. Plate unit 13 comprises base 12, upon which are disposed plates 14 and 16. Similarly, unit 27 comprises a base 26 upon which are disposed plates 28 and 30. The distance A between slots 18 and 20 is the same as the distance between plates 14 and 16. The length of the slots and height of the plate unit is slightly less than full waveguide height to facilitate production and to allow for variation in the waveguide dimensions without imposing extremely tight tolerances. When,

plates 14 and 16 are inserted into the waveguide, as in FIG. 2, a pair of inductive irises are formed.

The operation of the device will now be explained. As is well known in the art, the disposition within a waveguide of a transverse metal plate provided with an iris results in a portion of the wavepower incident thereon being transmitted and a portion being reflected. If the dissipation of the plate is small, the arrangement behaves much like apure susceptance. The

amount of protrusion of the plate into the waveguide largely determines the susceptance and, since the magnitude of the phase advance is related to the susceptance, the phase advance. The general subject of transverse plates and irises within a waveguide, including the susceptance introduced, is covered in Principles and Applications of Waveguide Transmission by Southworth, D. Van Nostrand, New York, 1950. Especially applicable are sections 8.5, 9.2 and 9.4. The insertion of plate 14 into the waveguide slot 18 creates an inductive iris and introduces a phase advance. In order to minimize the VSWR, a second iris is formed a predetermined distance A from the first iris. This second iris is created by the insertion into slot 20 of plate 16. The distance A is such that the round trip equals 180 (one-half wavelength) plus the phase advance introduced by the irises. If two plate units are used, as in FIGS. 1 and 2, the distance between them (that is, the distance between slot pairs in the waveguide), shown as dimension B, should be 1 k times the inter-iris distance for minimum standing wave introduced. In other words, for minimum standing wave and energy dissipation, B=1.5A.

The invention may be practiced in the following manner. After the phase shifter has been assembled in the well known manner, it is tested to determine the amount'of insertion phase in the magnetic reference state in which it is designed to operate. If the amount of insertion phase is within the allowable deviation, the phase shifter is left as it is. If the amount of insertion phase is beyond the allowable deviation the necessary number of plate units are inserted into the waveguide to bring the insertion phase within the allowable deviation. The waveguide can be constructed with the slots in the sides, and the plate units can be inserted only if necessary to correct the insertion phase. The amount of phase advanced introduced by each iris must be determined by the designer for the particular type of phase shifter, the type of ferrite material, the microwave frequency of the energy, etc. Maximum efficiency dictates that each plate unit will be the same as every other and can thus be mass produced prior to the production run of the phase shifters.

An alternative embodiment of the invention is shown in FIGS. 3 and 4. Waveguide section 100 has slots 1 10, 112, 114, 116, 118 and 120. Ferrite rod 130 is disposed within the waveguide section. Each plate unit has three plates in this embodiment. Plate unit 102 has plates 104, 106 and 108. Plate unit 122 has plates 124, 126 and 128. The distance from slot 110 to slot 112 is the same as A in FIG. 1 and the distance between the sets of slots (from slot 114 to slot 116) is the same as B of FIG. 1. The operation of the device is the same as that of the previously described embodiment. It differs in construction in that each set of slots has three slots and each plate unit has three plates. The middle slot 112 is midway between slots 110 and 114. Obviously, plate 106 is midway between plates 104 and 108. As can be seen clearly in FIG. 4, the middle plate in the unit may 6 therefore to be understood that, within the scope of the appended claims, the invention may be practiced otherwise than as specifically described.

What is claimed is:

l. A microwave phase shifter comprising:

a waveguide section;

a rod of ferrite material disposed within the waveguide section; and,

a plurality of two-plate sets, said plates of each twoplate set being transversely disposed, relative to the longitudinal axis of said waveguide, a first predetermined distance apart from each other within said waveguide section and said sets being disposed a second predetermined distance apart from each other,

said waveguide section being formed with a plurality of slots arranged in two-slot sets through which said plates extend, said slots of each two slot set being disposed said first predetermined distance apart from each other and said two-slot sets being disposed said second predetermined distance apart from each other, whereby the insertion phase shift of said microwave phase shifter is brought within an allowable deviation. 2 v

2. The microwave phase shifter of claim 1, wherein said first predetermined distance is equal to onequarter wavelength ofa microwave signal plus one-half of the phase change caused by said plates, and

said second predetermined distance is equal to one and one-half times said first predetermined distance.

3. A microwave phase shifter comprising:

a waveguide section;

a rod of ferrite material disposed within said waveguide section; and,

a plurality of three-plate sets, said plates of each three-plate set being transversely disposed, relative to the longitudinal axis of said waveguide, within said waveguide section, the middle plate of each of said three-plate sets being a first predetermined distance from either end plate and said three-plate sets being disposed a second predetermined distance apart from each other,

said waveguide section being formed with a plurality of slots arranged in three-slot sets through which said plates extend, the middle slot of each of said three-slot sets being said first predetermined distance from either end slot and said slot sets being disposed said second predetermined distance apart from each other, whereby the insertion phase shift of said microwave phase shifter is brought within an allowable deviation.

4. The microwave phase shifter of claim 3, wherein said first predetermined distance is equal to onequarter wavelength of a microwave signal plus onehalf of the phase change caused by said plate, and

said second predetermined distance is equal to one and one-half times said first predetennined distance.

5. The microwave phase shifter of claim 3, wherein said middle plate of each three-plate set extends into said waveguide section further than said two end plates.

6. The microwave phase shifter of claim 5, wherein said first predetermined distance is equal to onequarter wavelength of a microwave signal plus one-half of the phase change carried by said plates and said second predetermined distance is equal to one and one-half times said first predetermined distance.

7. A microwave phase shifter comprising:

a wave guide section;

a rod of ferrite material disposed within said waveguide section; and

a single two-plate set, said plates being transversely disposed relative to the longitudinal axis of said waveguide a predetermined longitudinal distance apart from each other within said waveguide section in order to minimize the VSWR,

said waveguide section having a single two-slot set through which said plates extend, said slots being said predetermined distance apart from each other, whereby the insertion phase shift of said microwave phase shifter is brought within an allowable deviation.

8. The microwave phase shifter of claim 7, wherein said predetermined distance is equal to one-quarter wavelength of a microwave signal plus one-half of the phase change caused by said plates.

9. A microwave phase shifter comprising:

a waveguide section;

a rod of ferrite material disposed within said waveguide section; and a single three-plate set, said plates being transversely disposed, relative to the longitudinal axis of said waveguide, within said waveguide section, the middle plate of said three-plate set being disposed a predetermined distance from either end plate,

said waveguide section having a single three-slot set through which said plates extend, the middle slot of said three-plate set being disposed a predetermined distance from either end slot, whereby the insertion phase shift of said microwave phase shifter is brought within an allowable deviation.

10. The microwave phase shifter of claim 9, wherein said predetermined distance is equal to one-quarter wavelength of a microwave signal plus one-half of the phase change caused by said plates.

11. The microwave phase shifter of claim 9, wherein said middle plate extends into said waveguide section further than said two end plates.

12. The microwave phase shifter of claim 11, wherein said predetermined distance is equal to one-quarter wavelength of a microwave signal plus one-half of the phase change caused by said plates. 

1. A microwave phase shifter comprising: a waveguide section; a rod of ferrite material disposed within the waveguide section; and, a plurality of two-plate sets, said plates of each two-plate set being transversely disposed, relative to the longitudinal axis of said waveguide, a first predetermined distance apart from each other within said waveguide section and said sets being disposed a second predetermined distance apart from each other, said waveguide section being formed with a plurality of slots arranged in two-slot sets through which said plates extend, said slots of each two-slot set being disposed said first predetermined distance apart from each other and said two-slot sets being disposed said second predetermined distance apart from each other, whereby the insertion phase shift of said microwave phase shifter is brought within an allowable deviation.
 2. The microwave phase shifter of claim 1, wherein said first predetermined distance is equal to one-quarter wavelength of a microwave signal plus one-half of the phase change caused by said plates, and said second predetermined distance is equal to one and one-half times said first predetermined distance.
 3. A microwave phase shifter comprising: a waveguide section; a rod of ferrite material disposed within said waveguide section; and, a plurality of three-plate sets, said plates of each three-plate set being transversely disposed, relative to the longitudinal axis of said waveguide, within said waveguide section, the middle plate of each of said three-plate sets being a first predetermined distance from either end plate and said three-plate sets being disposed a second predetermined distance apart from each other, said waveguide section being formed with a plurality of slots arranged in three-slot sets through which said plates extend, the middle slot of each of said three-slot sets being said first predetermined distance from either end slot and said slot sets being disposed said second predetermined distance apart from each other, whereby the insertion phase shift of said microwave phase shifter is brought within an allowable deviation.
 4. The microwave phase shifter of claim 3, wherein said first predetermined distance is equal to one-quarter wavelength of a microwave signal plus one-half of the phase change caused by said plate, and said second predetermined distance is equal to one and one-half times said first predetermined distance.
 5. The microwave phase shifter of claim 3, wherein said middle plate of each three-plate set extends into said waveguide section further than said two end plates.
 6. The microwave phase shifter of claim 5, wherein said first predetermined distance is equal to one-quarter wavelength of a microwave signal plus one-half of the phase change carried by said plates and said second predetermined distance is equal to one and one-half times said first predetermined distance.
 7. A microwave phase shifter comprising: a wave guide section; a rod of ferrite material disposed within said waveguide section; and a single two-plate set, said plates being transversely disposed relative to the longitudinal axis of said waveguide a predetermined longitudinal distance apart from each other within said waveguide section in order to minimize the VSWR, said waveguide section having a single two-slot set through which said plates extend, said slots being said predetermined distance apart from each other, whereby the insertion phase shift of said microwave phase shifter is brought within an allowable deviation.
 8. The microwave phase shifter of claim 7, wherein said predetermined distance is equal to one-quarter wavelength of a microwave signal plus one-half of the phase change caused by said plates.
 9. A microwave phase shifter comprising: a waveguide section; a rod of ferrite material disposed within said waveguide section; and a single three-plate set, said plates being transversely disposed, relative to the longitudinal axis of said waveguide, within said waveguide section, the middle plate of said three-plate set being disposed a predetermined distance from either end plate, said waveguide section having a single three-slot set through which said plates extend, the middle slot of said three-plate set being disposed a predetermined distance from either end slot, whereby the insertion phase shift of said microwave phase shifter Is brought within an allowable deviation.
 10. The microwave phase shifter of claim 9, wherein said predetermined distance is equal to one-quarter wavelength of a microwave signal plus one-half of the phase change caused by said plates.
 11. The microwave phase shifter of claim 9, wherein said middle plate extends into said waveguide section further than said two end plates.
 12. The microwave phase shifter of claim 11, wherein said predetermined distance is equal to one-quarter wavelength of a microwave signal plus one-half of the phase change caused by said plates. 